(a) Field of the Invention
The present invention relates to an organic light emitting device and a manufacturing method thereof.
(b) Description of the Related Art
Recent trends of lightweight and thin personal computers and televisions sets also require lightweight and thin display devices, and flat panel displays satisfying such a requirement are being substituted for conventional cathode ray tubes (CRT).
The flat panel displays include displays such as a liquid crystal display (LCD), a field emission display (FED), an organic light emitting device (OLED), and a plasma display panel (PDP).
Among the flat panel displays, the organic light emitting device is the most promising because of its low power consumption, fast response time, wide viewing angle, and high contrast ratio.
An organic light emitting device is a self-emissive display device that includes two electrodes and an organic light emitting layer interposed therebetween. One of the two electrodes injects holes and the other of the two electrodes injects electrons into the light emitting layer. The injected electrons and holes combine and form exitons and the exitons emit light as discharge energy.
The organic light emitting devices may be divided into two types, a passive matrix organic light emitting devices, and active matrix organic light emitting devices, based on the driving method utilized.
The passive matrix type of organic light emitting device includes a plurality of anode lines, a plurality of cathode lines intersecting the anode lines, and a plurality of pixels, each including a light emission layer, and the selection of one of the anode lines and one of the cathode lines causes light emission of a pixel located at the intersection of the selected signal lines. In contrast, the active matrix type of organic light emitting device includes a plurality of pixels, each including a switching transistor, a driving transistor, and a storage capacitor, as well as an anode, a cathode, and a light emission layer. The driving transistor receives a data voltage from the switching transistor and drives a current having a magnitude determined depending on the data voltage, and the current from the driving transistor enters the light emission layer to cause light emission having intensity depending on the current.
The thin film transistor such as the switching transistor and the driving transistor includes polycrystalline silicon (polysilicon) or amorphous silicon.
Amorphous silicon may be deposited under a low temperature, and thereby may be deposited on a substrate made of a glass having a low fusion point. However, the amorphous silicon has a low mobility of charge such that the thin film transistor having a channel of the amorphous silicon may have a limited performance. In contrast, the polysilicon may have a high mobility of charge such that the thin film transistor having a channel of the polysilicon may have a high performance. However, it is hard to deposit the polysilicon and the thin film transistor including the polysilicon may have a large leakage current. The leakage current may be increased when the surface of the polysilicon is damaged by an etching process, etc.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.